ANS:D - polyurathane

Polyurethane is a versatile polymer that belongs to the family of polymeric materials known as "thermosetting plastics." It is synthesized through the reaction of diisocyanates with polyols, resulting in a wide range of materials with diverse properties. Polyurethanes are widely used in various industries due to their excellent mechanical properties, chemical resistance, and versatility. Here are some key points about polyurethane:

1. Chemical Structure: Polyurethanes are formed by the reaction of diisocyanates with polyols. The diisocyanate molecules contain two isocyanate (-N=C=O) functional groups, while the polyol molecules contain multiple hydroxyl (-OH) functional groups. The reaction between these two components results in the formation of urethane linkages (-NHCOO-) in the polymer chain.
2. Types of Polyurethanes: Polyurethanes can be classified into two main categories based on their structure and properties: thermoplastic polyurethanes (TPUs) and thermosetting polyurethanes. TPUs are linear polymers that can be melted and remolded upon heating, while thermosetting polyurethanes undergo irreversible crosslinking during curing and cannot be remelted.
3. Properties: Polyurethanes exhibit a wide range of properties depending on their chemical composition and structure. They can be formulated to be flexible or rigid, soft or hard, and elastomeric or plastic. Polyurethanes are known for their excellent mechanical properties, including high tensile strength, abrasion resistance, and tear resistance. They also possess good chemical resistance and can withstand exposure to oils, solvents, and many other chemicals.
4. Applications: Due to their versatility, polyurethanes find applications in various industries. Common uses include:
   • Flexible foams for cushioning and padding in mattresses, upholstery, and automotive seating.
   • Rigid foams for insulation in buildings, appliances, and refrigeration.
   • Elastomers for seals, gaskets, wheels, and rollers in industrial applications.
   • Coatings and adhesives for surface protection, waterproofing, and bonding.
   • Fibers and textiles for apparel, footwear, and technical textiles.